Driving the Championship Winning Mercedes-Benz CLK-GTR

This FIA GT champion displays all the right breeding.

By
Dennis Simanaitis & Steve Millen

Mar 4, 2016

Stephane Foulon

From the November 1998 issue of Road & Track.

THE STREET/TRACK COMPARISON: Take a winning race car and its road going counterpart to the test track, assess their levels of performance and, most important, compare and contrast the characteristics that define each.

As recently as August 1998, this format seemed so logical.

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And then, in that issue of R&T, Senior Editor Kim Reynolds and driver Steve Millen brought together the Champion Racing Porsche GT1 and a road-going 911–and guess what: The race car had little in common philosophically with its sibling, except maybe its cupholders, and even these were specially fabricated from aluminum.

A new breed has evolved for the likes of FIA GT racing. This time around, though both Steve and I arrived at Hockenhiem in production Mercedes-Benz CLKs borrowed from the factory, we now knew enough to leave these perfectly competent road cars parked in the paddock. Simply put, there's no comparison.

(Background: The Mercedes-Benz CLK-GTR placed 1st in the 1997 FIA GT Championship and continued garnering laurels well into 1998. Driver extraordinaire and two-time IMSA GT champion Steve Millen and Engineering Edi­tor Dennis Simanaitis got some in depth experience with this car and its Persson Motorsport race team at Germany's Hockenheim circuit; Millen in the drivers seat and Simanaitis chatting up the engineers, technicians and support people who play important roles in the CLK-GTRs winning ways. - Ed.)

On the other hand, a fabulous surprise awaited us along pit row: For our photos, Klaus Seybold had brought out a Mercedes-Benz 300 SLR from the company's museum. And not just any 300 SLR, but no less than "722," the famous Stirling Moss-Denis Jenkinson Mille Miglia winner of 1955. In many ways, it's the 300 SLR that's the logical ancestor of our CLK-GTR.

A pair of champions. The 300 SLR dominated sports-car racing in the mid-Fifties.

Stephane Foulon

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Millen: The idea of driving the FIA GT1 Championship Mercedes-Benz stirred my imagination more than anything I had experienced since retiring from racing in 1996. I was especially keen to drive the car at Hockenheim, a race circuit new to me. At the edge of this German town about 45 minutes from Frankfurt, the track has an extremely fast layout running through the woods, then returns to a huge stadium and onto the pit straight. For our testing, we would use the shorter "club" circuit, eliminating the long stretches through the woods, but looping back behind the pits, 2.1 miles of interesting corners at varying speeds.

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And to add even more excitement to our day, we would share this track with the Mercedes-Benz/AMG factory team; there running-in spare components in preparation for the Le Mans 24-hour race barely a week away.

Like its newer Le Mans sibling, our CLK-GTR is built by Mercedes part­ner AMG. And, expanding on the theme of the Porsche racer that Reynolds and Millen tested in August, this car offers only a perfunctory resemblance to any road-going Merce­des-Benz. True, it sports a sleek rendi­tion of the classic grille— and even a three-pointed star— but the rest is dedicated race car.

FIA GT regulations dictated that a road-going example be built, though there was no obligation that it be sold. On the other hand, considering development costs, I can't help recommending a CLK-GTR road car as one of the automotive bargains of all time— even at its (FIA-capped) $1,000,000 price. (I'd multiply by 10 to get a mini­mum figure of actual cost.)

You'd be buying a swoopy-looking car indeed, its overall shape dictated by controlling the air around, into and through its carbon-fiber bodywork. Ducting at the front directs air to oil and coolant radiators and front brakes. Internal flow-control is evident in vanes and baffles beneath the bodyshell.

And, curiously, there are louvers at the front-brake airflow exits, just aft of the wheel openings. However, these are dictated by regulation, not aerodynam­ics. The FIA doesn't want its GT class to appear as simply Formula 1 cars with downforce-generating "fenders." So, with bodywork fully fitted, there can be no mechanical parts, wheels or rubber visible from the rear. Hence, the louvers (and I score it GT Designers 1, FIA 0).

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Like other FIA GTs, the CLK- GTR has a flat bottom between wheel centerlines; this regulation to obviate extensive downforce tunneling. There's a neat tidbit here as well: Flat-bottom cars are extremely sensitive to pitch, and radically low ride-heights are one technical response. A competitor complained about the CLK-GTR pushing this beyond the regulations, and the FIA came up with the idea of a wood­en plank mounted beneath each car to insure that the scrutineered ride-height be maintained. The plank is about 1.2-in. thick, weighs 88 lb., and if it shows any scratches in post-race inspection, you're out.

Mercedes-Benz

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Initially, the plank cost something like 2 seconds a lap, but clever aerodynamicists have regained much of this. Ironically, the competitor that com­plained is no longer officially racing in the FIA GT Championship. Not to spread rumors, but it's based in Mu­nich and Munich is in Bavaria, if you get the drift of my meaning.

While in a regulatory vein, there's another FIA GT requirement indicat­ing just how environmentally sensitive racing has become: Measured at 0.5 meter (about 20 in.) and an angle of 45 degrees from the exhaust, the noise level can be no more than 110 dBA at 6300 rpm or three-fourths of redline, whichever is greater.

Not to worry, race enthusiasts, be­cause 110 dBA is LOUD.

But enough of regulations for a mo­ment; what's the CLK-GTR like to drive? First, you should recognize that, unlike your Engineering Editor, Steve Millen has the stature and build of a gymnast. But I'll let him tell it.

Because of the rake of the windshield, the angle of the door opening and the tightness of the cockpit, I need to put on my helmet before maneuvering in. I note that the 1998 Le Mans car has gullwing doors opening toward the center of the roof, no doubt speeding up driver changes enormously.

Once in the form-fitting seat, I find my legs angled off toward the center of the car, my hips off to the side; that is, I'm not sitting straight inline with the car. This isn't apparent when I 'm driving, though afterward there's a stiffness in my shoul­der that may be explained by the skewed driving position.

Like everything else about the CLK- GTR, its interior is carefully laid out, neat and well finished. The lever for the 6-speed sequential gearbox is a most prominent feature, its thick grip sticking straight up in the middle of the cockpit, its large-diameter shaft operating a cable to the gearbox. We're told that this cable gets replaced every 1500 miles or so, to main­tain reliable actuation.

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A first for me is driving a racing car with an airbag-equipped steering wheel. The wheel also has three buttons, one for pit communication, the other two giving extremes of fuel flow— one is for power and overtaking, the other is for stretching the fuel supply. At the top of the steering wheel are four green lights embedded in the leather rim, these to identify whether any wheel is locking under braking. I'm told that's very easy to do without other­wise realizing it. There's also a digital display on the dash that tells you what gear you're in, helpful when you're picking your way around an unfamiliar circuit.

To my right are the communications radio and the car's electronics, with sur­prisingly little of the latter. We're told that back in DTM days (German Touring Car Championship, which developed into one of the more outrageously complex forms of racing), the electronics resided in a box that was 2 x 2 x 1 1/2 ft. What's more, those components generated so much heat that nearby cockpit temperatures soared beyond 160 degrees Fahrenheit.

Fortunately, GT cars are a lot simpler than those running in DTM.

Stephane Foulon

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In fact, FIA GT cars are missing many technical enhancements taken for granted on the road. Neither ABS (in GTl) nor any form of traction control is allowed. There's no drive by-wire throttle control, no active sus­pension, not even any driver-adjustability of anything beyond simple fore-aft brake-bias. Real-time teleme­try is prohibited during the actual events, though it's an important fea­ture in testing and development. Also, onboard data-logging with subsequent download is allowed.

Steve fires up the CLK-GTR's V-12 powerplant, already fully prepped by the team, and goes out to learn his way around Hockenheim.

Obviously, to test a racing car in the middle of the season is a big responsibility: I 'd better not get in over my head. So I sneak up on the speed with 5-lap increments, pushing a little harder each time.

It's necessary to push, because otherwise I won't have a good impression of low- or high-speed balance, or of the effort required to race this car.

On this first stint, I 'm particularly im­pressed by the V-12's smooth progression of power. Throttle response is instantaneous, especially in contrast with turbocharged race cars I've driven. It's my first experience with a sequential gearbox, but it upshifts nicely with just a slight easing of the throttle and a firm tug of the lever.

The understeer is fairly strong; maybe I 'm not loading the chassis enough. I 'm still learning my way around the circuit. After each stint, I 'm debriefed by Persson Motorsport personnel, and then I get out, pause and consider what I've learned.

The bodywork comes off the GTR for a check, and this gives me an op­portunity to look things over. There's a central monocoque of carbon fiber. The car's mid-engine acts as a semi­-stressed member, with triangulated tubular structures augmenting its sup­port of the rear suspension. At either end, unequal-length A-arms locate the hubs while pullrod-actuated coil springs support the load. Shock ab­sorbers, anti-roll bars and ride height are all adjustable (but not from the cockpit). The brakes are carbon fiber, allowed in GT1 but not in GT2 (where conventional ABS is permitted).

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The CLK-GTR's V-12 shares its 5987-cc displacement, 89.0-mm bore and 80.2-mm stroke with the big Benz powerplant, but you wouldn't mistake one for the other internally. The GTR's connecting rods are titanium, its compression ratio is 12.0:1 (versus an S-Class's 10.0, for instance), and it produces an estimated 600 bhp at 7000 rpm (versus an S's 389 at 5200).

Stephane Foulon

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What's more, even this output is regulation-rigged: FIA GT engines all breathe through intake-air restrictors, their diameters set to encourage com­petition among cars of various displacement, weight and even different degree of factory involvement. True privateers, for example, are allowed larger-diameter restrictors.

"Without its restrictor," I was told, "this engine would produce some 800 bhp—but not necessarily for long...." And, of course, durability is of great importance in endurance racing.

Onboard fuel is limited to 100 liters (26.4 of our gallons). I'm told scruti­neers take into account the combined volume of fuel cell, lines, any reser­voirs, catch-tanks, etc. (Do I sense another neat loophole slammed shut?) The spec-fuel is unleaded gasoline, with a maximum of what we'd call 96 pump-octane. Refueling is by gravity-feed-only from a specified height. And, before you even suggest it, the fuel cannot be stored at a temperature less than 10 degrees Celsius below am­bient. On the other hand, top teams are seen to wrap their pit holding tanks in insulating material, so it's cer­tainly no warmer than ambient either.

This fuel gets gobbled at a rate of around 4 mpg, giving the GTR a range between pitstops of a bit more than 100 miles. Persson Motorsport driver Marcel Tiemann tells me that a typical stint would be twice this, with a tire change likely at the same time. It's best, he notes, not to send a fresh driver out on worn tires.

A personable young man of 24, Marcel is a rarity in international rac­ing these days, in that he didn't begin in go karts. His background, instead, is in Formula Renault and Formula 3. What's more, he even has a bank traineeship under his belt, though I suspect he won't be calling on this ex­pertise for many years.

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Endurance racing makes for interesting nuances in driver psychology. Often, for example, an older, experi­enced driver will be teamed with a young hotshoe. Also, because of fuel-consumption pressures, the left-foot braking common in Formula 1 is con­sidered bad form here.

Once Steve has thought things over, he and Marcel share information in a Driverspeak that's not really appreciat­ed by the rest of us. Then Steve ma­neuvers into place for another 5 laps.

Mercedes-Benz

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This time, I'm familiar with the gearbox and throttle sensitivity, and I 'm ready to get down to business. Racing cars do not behave well unless you brake as late as possible, really loading the suspen­sion. This is the only way the tire patch ultimately produces its best adhesion.

The brakes have no assist, but these AP calipers clamping carbon rotors have a terrific response without much effort re­quired. The steering is power-assisted and it has a delightful feel; very smooth with little effort. I can appreciate that this is a proper endurance car developed for long stints at the wheel.

I push harder on these laps and explore the GTR's limits of braking and handling; still not consistent enough but the rhythm is coming.

What with the Le Mans cars circu­lating as well, we won't have opportu­nity to set out our test equipment here. Fortunately, though, Persson Motor­sport shares a complete database of the GTR's capabilities, and it's possible to generate our own virtual data panel.

The car's Hockenheim gearing is rel­atively short, giving a top speed of (only!) 191 mph at 7800 rpm, this modest redline reflect­ing an endurance-racing in­tent. The team estimates that the GTR reaches 60 mph from a standing start in 3.4 seconds and takes 9.4 to cover 400 meters (just 8 ft. shy of our quarter mile). Given the steepness of this ac­celeration curve, I'm confident in extrapolating a speed of 137.0 mph as the GTR travels past our virtual quarter-mile marker.

There are neither slalom nor 80-0/60-0 braking data; this, because an FIA GT car rarely does anything even vaguely resembling these two exercises and the team's database is devoid of relevant information. And not that our lateral-acceleration entry of 1.7g evidently profits from ground effects, a phenomenon not generated at typical speeds around our standard 200-ft skidpad.

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On the other hand, Marcel Tiemann plays road-test-editor-for-the-moment and records our interior noise data: 91 dBA at what passes for idle, 110 dBA at constant throttle and 90 mph, and 120 dBA on redline upshift. Last, playing FIA-official-for-the-moment, I check that the CLK-GTR satisfies its FIA-mandated exterior-noise 110 dBA limit. It passes—piece of cake!—at 105 dBA.

And then it's time for Steve's con­cluding stint.

For my final 5 laps, I drive harder still and it all comes together. What a real thrill! The car's handling, power and brakes are all in concert. It 's very satisfy­ing and leaves a great impression of this fabulous CLK-GTR.

It's always fun to watch a professional at work. Steve's last 5 laps are all within 0.2 sec. of each other, the CLK-GTR snarling its way around Hockenheim in a most impressive manner. It's an evident case of excellent breeding—both in driver and in car.

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